Editors' Blog

Bosch Sensortec recently announced a new environmental sensor, the BME680. It actually builds on prior devices. The first was simply pressure and temperature; the next added humidity; and the BME680 adds gas sensing to that.

We’ve looked at a variety of ways to do analyte detection in the past, so I was curious as to which of those Bosch used in this device.

And the answer is: none of the above.

The humidity is detected by a polymer that adsorbs water and affects a capacitance; then again, that’s not what’s new in this device.

The gas sensing is not as specific as what we’ve looked at. It’s a single membrane onto which a number of different analytes can adsorb. I wasn’t able to get much more detail than that; in general, they detect volatile organic compounds (VOCs) and alcohol. It’s a consumer-friendly sensor that doesn’t give specific numbers for specific gasses; it simply says whether or not there’s an issue with the air. It’s driven by the indoor air quality (IAQ) guidelines that regulatory bodies issue.

So while it may not be as selective or specific as what some of the other techniques provide, it is targeted at mobile devices, so size (3-mm square) and low power are key deliverables. And, realistically, it’s unlikely that most phone users would do much with specific analyte numbers anyway.

One trillion. 1,000 billion. That's a big number. But that's how many semiconductor devices we're on track to produce and ship in 2017. This according to IC Insights and its latest market-research report. Obviously, that total includes just about everything that could conceivably be considered a semiconductor device, including digital chips, analog chips, opto sensors, and more. To reach that impressive sum, the company projects 10% growth in unit shipments this year, and another 11% growth next year. Good times.

Cavendish Kinetics recently made an announcement regarding their ongoing reliability testing for their MEMS-based antenna-tuning technology.

We’ve talked about this tuning concept before (albeit with a different name); the short version is that, with all of the different bands that cell phones need to access, it becomes difficult to optimize the antenna for all of them in the limited space available. So the idea is that you have a capacitor array switched by MEMS elements, and you can then change up your filter with each band to optimize accordingly.

We also looked in more depth at Cavendish Kinetics’ particular approach before, including a description of work they’ve done to limit the range of switching capacitor plates to keep them from over-traveling or slamming too hard against stops.

But, such assurances aside, the question phone makers have remains: how reliable are those MEMS elements? How many times can you switch them before they fail?

Well, according to Cavendish Kinetics, a lot. Like, 100 billion cycles and counting.

And who needs that many cycles? Well, no one, actually, according to them. But, hey, when you’re on a roll, might as well keep it going to put any lingering doubts to rest.

In my mind, I make some comparison to a gyroscope, which has to be in constant motion. Where there is literally a mechanical member moving (as opposed to techniques involving internal resonances), you can add up those movements pretty quickly. Billions aren’t hard to attain. Even if the frequency was a slow 1 kHz, you’d hit a hundred billion cycles in just over 3 years.

But here’s the difference: with the capacitor array, the elements move only when you change configuration. While in use in a particular configuration, the switches are static. If you changed configurations every second, then in three years you’d get roughly (just under) a billion switching events. Which means it would take running the system that aggressively for on the order of 300 years to get to a hundred billion cycles.

I’m thinking the battery would probably wear out first. (And it suggests that their test runs somewhat faster than 1 Hz…)